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This is first step for the Solar power system design, mark down your load list. We are doing this step for calculating the solar panel and battery power.

Solar power system design Step1-Load list

Why do we need load list?

This first blogs is appropriately called step one loads list. 

Figuring out how much power you need is a critical step that many people try to skip, designing a solar system without knowing your loads is like being asked,

How much gas do I need to drive without knowing what type of vehicle or how far you're driving?
solar power system design - InkPV
For instance, if you needed to use a welder for a project, it may not make sense to design the whole system to be able to accommodate a tool that is only used once a year. 

Having a generator available for occasional use makes good sense. Keep this option in mind when designing your system. This video series will cover the major steps of designing an off grid system. 

Let's start with step one, analyzing your load. Let's go of the steps to determine the amount of power you need. Let's start with the loads analysis, unlike a grid type system where you can just base a system on how much power you want to upset, and then get the rest from the grid. 

An off grid system needs to provide all of your power. With an awkward system, you need to take a good look at what you are powering and how long you need to power it. 

Going off grid often takes changes to your lifestyle. It's not just as simple as saying, I'm tired of paying the electric company, I'm taking my whole house off grid,
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You have to figure worst case scenarios, winter time, little to no sun for days, unless you're in a climate as long sunny days, all year round or this is for a seasonal house.

Most people who are doing a year round office system will have a generator available to pitch in the winter. I read a quote from an off greater who said, if it's gonna be a sunny day, I can cook waffles for breakfast. If it's cloudy, I have a bowl of cereal. 

When designing the system, you can't just say it's an average size system. No such thing. You also can based on square footage of a house or cabin. 

One cabin may have air conditioning and electric stove, water heater, electric washer, and dryer, fridge and freezer. The other may have LED lights in a laptop, which one is average?
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Who is to say, do you think the same system will work for both cabins, even though they are both the same physical size? 

No. You need to make a Complete list of every electrical device you'll be using, how much power uses and how long each day it'll be on? 

Don't forget anything. All you listed equipment will have power label on it. Since votes times amps equals what? 

You should be able to get all the Information you need off the labels.

How to do the load list

Here's some examples from just walking around my house. You can see some do list, the watts, and some list of voltage range, some have the arms, some list, the DC voltage, and am used from a power block that's converting the ac voltage to DC to charge the onboard battery. 

If the label only list the volts and amps, but not the watts, you can multiply the volts times amps to get watts. Once you have watts, you then multiply the watts times hours a day that it's on. You get the 1 hours a day. 

This is not perfect as the listing may just have the startup current and not the continuous power, but it is a starting point. If the voltage is listed in DC instead of ac you will still multiply the DC volts by the apps to get the watts.

 If the voltage listed is a range like a hundred, 240 volts, you use the voltage that is used in your area, for instance, 120 volts for North American outlets. 

Some loads like refrigerator or pump or furnace fan are not on continuously and have a high surge when it turns on making it difficult to determine how much accumulated power or 1 hours it uses throughout the day.
solar power system design - InkPV
If it is energy star rated, you can find the energy star label, either on the appliance itself or on the energy star website. 

If it is not energy star rated and you're looking to power with solar, it may be worth it to replace it with an energy star fridge. 

The reduced amount of power than energy star appliance uses may pay for itself. When you look at how much it would cost power with solar.

The energy star label will tell you the average annual kilowatt hours used. From there. 

You can simply divide it by the number of days in the year, 365, to see how many 1 hours it uses in a day. In this example, 383 kilowatt hours a year divided by 365 days in a year.

 It was 1 . 049 kilowatt hours a day. You can multiply that by a thousand to determine how many 1 hours a day as a kilowatt is 1,000 watts.
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How to deal with the information?

Right now that we know how much power each device is using. 

What do we do with that Info? Using a load calculator can help you create the loads list. 

This calculator is available on all these cheat sheet to use it. 

You enter the appliance name, quantity, and how many wants it is in ac or DC? If it's ac, if it plugs into a wall outlet, if it's DC, it runs off a battery like a cell phone car charger. 

On at the same time indicates that the system needs to be big enough to power those devices simultaneously. 

For example, you have no control over when your fridge compressor will turn on or when you will pump will. 

But you can control when you turn on a light. So if there's a chance that multiple devices may be on at once, you must select on at the same time, that will help you determine how big of an inverter you need to handle that power if they all turn on it once.

What is inductive load?

solar power system design - InkPV
solar power system design - InkPV
Some devices also have a high momentary surge, like a fridge or motor, it can use 2 to 4 times as much power for a few seconds when it first turns on, 
you need to keep track of that as well. 

Because if your inverter cannot handle that surge, the device may not be able to turn on, or you could damage the inverter. 

You need to enter how many hours a day advice will be on. If it's less than an hour, do the decimal equivalent? 

For instance, half hours . 5, whether you're using the calculator or joining the list by hand, all of the water hours get added up to show the total amount of power you need to generate for that day. 

That's it for the first video in this series of designing an off grid pv system. You can go to our website to use our loads list calculator to calculate your own loads.
Wang has over 10 years of experience in off-grid projects. And know how to wire the system well. Making every installation step easier.

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